Flat spray nozzles produce impact sprays, with narrow angles.
They are very efficient for use in the "Pre-Treatment" process that many products go through before paint dipping applcations. "Pre-treatment" ensures that product is clean and often applies protective coatings such as phosphate, chromate or a paint primer.
- A large number of different products are cleaned this way
For exampke, car bodies and car panels, washing machine, refrigeration and dishwasher csing all pass through a similar pre-paint finishing proces
The process almost always zoned with the first zone being a de-greasing or chemical detergent operation, or "knock-off zone"
In some plants, for example, the car industry, the first de-greasing operation is split into two zones
The first cleaning zone is often called the "knock-off zone"
The flat spray nozzle with high pressure and high volume means that large pieces of waste material can be removed easily as the product passes through the cleaning zone.
A second, de-greasing znone is sometimes used to remove smaller pieces of waste from the product
More zones are usually used to wash and phosphate or chromate dip the product before a primer is applied ready for painting
The product, whether a car body or smaller item such as washing machine casing, is moved through the cleaning system using a moving hanger as shown in the diagram. Quick couplers are used to attach the manifolds to the supple pipe so that they can be easily removed for cleaning or replacement when the car body design changes. Removable end caps allow the manifolds to be cleaned more easily.
The flat spray nozzles used in this application are as follows:
The spray angle depends on the distance from the nozzle to the product but typically 50° or 65° are used on AC and 35° on TJ nozzles
- In a car body plant, for example, the AC nozzles are used for most requirements
The TJ nozzles are used to spray the underside of the car body and have a reach of over 1 metre
The use of Ball Swivel, spray clip eyelets or AP Ball Jets allows the spray direction to be altered to fit different product needs
Most installations use stainless steel nozzles, however there is a general move towards the use of plastic materials in modern plants, because of cost and maintenance
This is mainly because of the esae of nozzle cleaning and maintenance given by the plastic design
The most common material used for plastic nozzles and threaded balls is polypropylene with pipework being fabracated from cVPC mateiral
All plastic nozzle materials (AP Ball Jets) used in paint plants must be specified silicone fre
Silicone is used on the mouldingof rubber components and if it is not removed it will contaminate the metal surfaces being cleaned
If a metal surface becomes contaminated with silicone, paint will not stick to it.
When the nozzle fitted is tainless steel, it will not be changed very frequently
Most manufactureres are trying to convince end users that plastic is a better materials
- it is more suitable and more cost effective
Moulded plastic itesm are such less expensive ad can threefore be changed more often
The recommended change period is between three and six months
In the phosphate cleaning zone it is much more chemically aggressive and there is a need to change nozzles as frequently as every month
Worn nozzles do not currently spray the product.
Eductors are used in dip tanks to circulate the liquid
The eductors are used to cause a flow of the liquid contained in the dip tank - this effect is called agitation, and is necessary to keep solids in suspension. Agitation is required to make sure that the liquid is well circulated and completely covers the product
Tanks are emptied 1-2 times a year and some tanks have acid wash applied
The dip tanks used in the car industry are usually between two and three cars in length.
Each tank will have up to thirty eductors fitter depending on tank size. The eductors are fitted into the tank on a ladder pattern as shown in the diagram.
The most common size of eductor used in the car industry is 3/4 inch BB300
This nozzle gives a liquid turnover of 3:1. This means that the volume of liquid drawn in is about 3 times the volume of e liquid pumped through the nozzle orifice.